1. Field of the Invention
Embodiments of the present invention relate generally to graphics system hardware and more specifically to a single-to-multiple display adapter utilizing a single cable construction.
2. Description of the Related Art
A typical computer system includes, without limitation, a central processing unit (CPU), a graphics processing unit (GPU), at least one display device, and one or more input devices, such as a keyboard and a mouse. In many common applications, users require two or more display devices to be attached to a single computer system. The display devices are typically attached to the computer system via video cables that connect to one or more graphics adapter cards, installed within the computer system.
To maximize connector area efficiency, a host adapter card may incorporate a high-density connector to transmit two or more standard video signals. The two or more video signals available through the high-density connector need to be separated out into individual standard video connectors in order to properly connect to associated display devices. A cable assembly is typically used to attach two or more display devices to the high-density connector. The cable assembly commonly includes a matching high-density connector and two or more independent cables emerging from the matching high-density connector in a structure known as a “pig-tail.” The loose end of each independent cable is attached to a standard video connector that is configured to deliver a video signal to a single-channel video cable. The single-channel video cable includes a sufficient number of conductive paths to deliver a standard video signal to from a first standard video connector to a second standard video connector, which may be attached to a display device.
The pig-tail cabling structure facilitates the use of high-density connectors, while preserving compatibility with existing single-channel cabling regimes. However, the pig-tail cabling structure is also quite bulky at the exit point of the matching high-density connector and adds an additional cable end connector in the video signal path. Each signal within the cable end connector typically traverses an ungrounded span from the shielded cable to a predefined pin on the connector. This ungrounded span degrades the overall signal integrity of the video signal by interposing an impedance mismatched span in the signal path. Each impedance mismatched span in the signal path introduces noise in the transmitted signal, reducing overall system performance.
One approach to minimizing signal degradation in a pig tail cabling structure is to use high quality, low-loss components and cables. For example, high-quality low-loss cables may be used along with cable end connectors designed to match impedance and minimize connector injection loss. While this approach may help, significant signal degradation nonetheless occurs in the ungrounded span from the cable end to the connector pins. This signal degradation is becoming an important limiting factor in video cable assembly performance as general advances in video technology drive video signals to higher speeds, making the signals more susceptible to impedance mismatches.
As the foregoing illustrates, what is needed in the art is a mechanism for separating video signals from a high-density connector to individual standard connectors that also minimizes impedance mismatching effects.